Things that were not immediately obvious to me

Working with SQLite on the iPhone, I ran across a strange (to me, anyway) interaction between prepared statements and transactions. This interaction (which I’m not sure it would be fair to call a “bug”) was causing DB writes to take effect only while my app was running, without being committed to disk. This, of course, was not the desired behaviour, but fortunately it could be corrected.

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Although Apple’s documentation doesn’t make too much of the point, the iPhone offers full support for SQLite. If you’re comfortable with DBs, this can be a timesaver, even for some problems for which a DB might seem like overkill. (In iPhone OS 3.0 and up, Core Data is also supported.)

This post offers a good introduction to the topic. Pay careful attention to the discussion of the libsqlite3.0.dylib file, as it’s the only really non-obvious part of getting started.

Incidentally, is it just me, or are there a disproportionate number of Aussie iPhone developers/resources?

Editorial note: This is the first of several posts covering shiny button backgrounds. I’m breaking the topic up in order to keep the posts shorter. Also, today’s post is up a little late, due to another project. My apologies.

If you look carefully at the glossy buttons used in native iPhone apps (e.g. the Stopwatch Clock app, or the “slide to unlock” control) you’ll see that they have a rather complex border. They appear to sit in a “well” comprised of a several pixel wide “moat”, surrounded by a one pixel wide “edge”. Both the moat and the edge have gradients applied to them.

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When using hierarchical table views (e.g. with a Navigation Controller) to enter or edit information, the proper sequence of UI events can be surprisingly subtle. Consider what happens when you edit a phone number in the Contacts app:

• You click on the number (in the “Edit” mode of the “Info” view)
• The row highlights blue
• The “Edit Phone” view scrolls in from the right
• You change the number, and press “Save”
• The “Edit” mode of the “Info” view scrolls in from the left
• The row highlight fades out

Note that when the “Edit” mode of the “Info” view scrolls in from the left, the edited number field shows the new value, before the highlight fades out. This is a tricky effect to achieve.

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Yesterday, I made reference to the contentVerticalAlignment property of UIControls. Upon further examination, it may not be such a good idea to use this property, for a somewhat surprising reason. If you look carefully at the screenshot to the left (click for a full-size view) you’ll see that the non-first-responder UITextFields are blurry.

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Editorial Note: I’d been planning to write about glossy button backgrounds today, but I appear to be buttoned out. I’ll pick the topic up again by Friday, but, for now, something lighter. And shorter.

Let’s say you want to adjust (horizontal) text alignment in a UITextField. No problem – you use the textAlignment property. Now, suppose you want to control vertical text alignment in that field …. there doesn’t seem to be a property for that.

Well, there is, but it’s buried in the UIControl ancestor class. The contentVerticalAlignment property is the one you want. I suppose it’s not unreasonable to put this property here, but since it took me a while to find it, I thought I’d mention it.